Please refer to the link at:
http://www.biotopics.co.uk/nutrition/lipase.htmlENZYMES AND DIGESTION
- The action of lipase on fats
The substrate used in this experiment is fat, which makes up about 3.9% of full cream milk. A small amount of alkali has been added in order to change its pH and for experimental reasons.
The enzyme lipase is from the mammalian digestive system.
Depending on the conditions in the surrounding medium, it may break down (digest) the fat to fatty acids and glycerol.
During this practical session you will be seeing the lipolytic effect of the enzyme (as well as the contribution made by the emulsifying effects of bile salts).
The fatty acids which are among the products of the reaction above will react with alkali to cause a change in pH, which will make the indicator phenolphthalein change from pink to colourless.
Preparation of a series of different combinations
Make sure that pipettes are not contaminated by placing them in other liquids.
- Do not use pipettes for any other purpose.
1) Place 6 test-tubes in a rack, and label them 1-6.
2) Using a single 3ml pipette (twice) put 6 ml of alkaline milk into tubes 1-6.
3) Using a single (smaller) pipette, add 0.5 ml phenolphthalein into tubes 1 to 5 BUT NOT 6.
4) Using a single different pipette, add 1 ml bile salts into tubes 1 , 2, 3 and 6 ONLY.
5) Using yet another pipette, add 1 ml lipase into tubes 1, 2, 4 and 6 ONLY.
6) Record the colours of the contents of the tubes in the table below - in the row labelled "colour at start."
7) Transfer tubes 2-6 to a water bath at 37°C, and leave them for some time. In the meanwhile, you have the opportunity to carry out the test procedure overleaf which will tell you more about these substances.
8) At regular intervals examine the tubes and look for signs of colour changing from pink to whitish. Record the final colours of the contents of the tubes in the table below - in the row labelled "colour at end."
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